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Other vernacular names. Semipalmated goose, pied goose, black-and-white goose; Spaltfussgans (German); oie pie (French); gans overo o pintado (Spanish).
This is the only species of true waterfowl with only partially webbed feet. Adults of both sexes are black on the head, neck, wings, rump, and tail, and white elsewhere. The bill is long and straight, with a well-developed nail at the tip; as in swans, the head is featherless back to the eyes. Females resemble males but are somewhat smaller, lack an enlarged bony crown, and have a higher-pitched voice. Adult males have an elongated trachea that loops downward between the breast muscles and skin and can be felt through the skin; adult females and immature birds lack this feature. Immature birds also have more mottled and grayish plumages than do adults. There are no seasonal variations in plumage. In the field, this goose-sized bird can be readily recognized by its distinctive black and white plumage, its long legs, and its honking, gooselike call. In flight, the slow wing beat and rounded wing outline produce a somewhat vulturine appearance; in the wild the birds usually occur in family-sized groups or larger flocks.